a. Field of Invention
The invention relates generally to automotive instrument panels having automotive Passenger Side Inflatable Restraint (PSIR) components, and more particularly, the invention relates to a two shot automotive PSIR chute.
b. Description of Related Art
Automobiles are commonly equipped with airbags for reducing driver and passenger injuries in the case of an accident. Automobile airbags are generally located in areas where a driver or passenger would potentially contact an automobile interior in the event of an accident. Airbags can reduce injuries by providing a substantially non-solid surface for the driver or passenger to contact, as opposed to the generally solid surfaces of the automotive interior. Although the functionality of the airbag is greatly valued, the visual appeal of the instrument panel, and invisibility of the airbag system are also of value to automobile manufacturers and consumers alike, as it leaves the general surface styling uninterrupted.
In order to install an airbag, the airbag is generally folded into a module that is installed into and behind an automotive instrument panel component. The module housing a Passenger Side Inflatable Restraint (PSIR) is generally installed on the underside of an instrument panel, with a PSIR chute between the instrument panel and PSIR module. The instrument panel generally has pre-weakened lines that are invisible when viewed from the top, forming one or two doors allowing the airbag to release therethrough. A PSIR chute assembly is typically bonded to the instrument panel and generally includes chute doors behind PSIR doors, where the PSIR doors line up with the pre-weakened lines on the instrument panel. For example, FIG. 1 is an environmental perspective view of an automobile interior 10 having an exemplary instrument panel 12 and windshield 13, where the instrument panel 12 contains on its underside a sectional view of a conventionally mounted PSIR chute assembly 14.
FIG. 2 is a diagram illustrating exemplary deployment characteristics of a typical PSIR air bag. Referring to FIG. 2, a passenger P is positioned on the passenger side of an automobile interior in front of instrument panel 12 and windshield 13, and deployed airbag 15 must open at a substantially oblique trajectory T relative to PSIR rearward door 18 and PSIR forward door 20. Referring to FIG. 3, a sectional perspective view of a conventional PSIR chute and airbag module assembly 14 is shown. Chute and airbag module assembly 14 is located behind instrument panel 12 having an instrument panel outer layer 16 and behind PSIR rearward door 18 and PSIR forward door 20 and coupled at center score line 26.
PSIR chute assembly 14 includes a first chute hinge 22 hingedly connected to a chute rearward door 28 and includes a second chute hinge 24 hingedly connected to a chute forward door 30. Chute rearward door 28 is located substantially directly behind PSIR rearward door 18, and chute forward door 30 is located substantially directly behind PSIR forward door 20. Chute assembly 14 further includes chute sidewalls 32a, 32b, and chute end wall 33 connected by connectors 31, and contains and guides an airbag 34. Airbag 34 is contained within chute sidewalls 32a, 32b, and chute end wall 33, and is deployed through chute doors 28, 30 and PSIR doors 18, 20 upon deployment. Chute assembly 14 further includes a first chute flange 36 and a second chute flange 38. Chute assembly 14 is attached to an inner layer 40 of instrument panel 12 at chute doors 28, 30 and chute flanges 36, 38.
A conventional single layer injection molded instrument panel is typically made of a first material comprised of a hard plastic material which is somewhat brittle at cold service temperatures (less than 25° Fahrenheit), such as thermoplastic polyolefin (TPO), blended polypropylene material, polycarbonate, polyethylene based polyolefin plastic, urethane or another suitable plastic. FIG. 3 shows a conventional construction of a typical single shot injection molded chute where chute doors 28, 30, chute hinges 22, 24, chute sidewalls 32a, 32b, chute end wall 33, and chute flanges 36, 38 are made of a second material 44 comprised of a tough ductile material, such as a polypropylene or polyethylene blended with rubber or a polycarbonate or another suitable ductile material.
The thermal expansion properties (a substance's tendency to change in volume in response to a change in temperature) and elastic modulus properties (a substance's tendency to be deformed elastically when a stress force is applied to it) of the conventional PSIR chute assembly material and the conventional instrument panel material are different and can result in warping, distortion, and uneven compression when the chute assembly and instrument panel are exposed to temperature changes and stress forces. For example, a known method for attaching a PSIR chute assembly to an instrument panel may include vibration welding the PSIR chute to the instrument panel. Vibration welding joins components by “rubbing” them together, creating heat through the friction, melting the connection points, and applying/holding pressure until the components cool together, thereby welding the components at the connection points. Welding melts the connection points between the instrument panel and PSIR chute assembly, thus causing the volume of the melted instrument panel and PSIR chute material to shrink relative to the other surrounding material and to shrink unevenly relative to each other. During the cooling process, there is known to be further shrinkage/deformation of the materials. As such, during the known vibration welding of an instrument panel and a PSIR chute assembly, there can be visible deflection of the instrument panel at the connection points between the components caused by uneven shrinkage during the cooling process due to the materials having different thermal expansion and elastic modulus properties. The cooling process induces thermal shrinkage and stress in the connection points that can result in compression in such connection points and tension in the opposite visible areas of the instrument panel outer layer.
Moreover, known methods of constructing instrument panels and PSIR chute assemblies may result in damage to the outer layer of the instrument panel which often has a surface grain stipple. Such methods may produce high local loading that results in increases in the gloss level on the outer layer of the instrument panel stipple that is unacceptable without paint or additional cosmetic application procedures.
It would therefore be beneficial to provide an economical and efficient two shot automotive PSIR chute and method that addresses the issues with existing devices and methods and that minimizes and/or eliminates one or more of the above-identified deficiencies.